FIG. 1 shows such a radio communications terminal 10, essentially comprising a receiver antenna 11, a screen 12, typically a liquid crystal display screen, a navigation key 13, and a keypad 14. The terminal 10 also has a battery 15 integrated therein and a connector 16 for connecting the battery to a battery charger. Finally, the terminal 10 has a printed circuit IMP for receiving all of the circuits of the radio communications terminal, which circuits include various types of microprocessor chip.
In conventional architecture for GSM type radio communications terminals, the screen of the liquid crystal display screen type is controlled by a microprocessor implemented on a chip referred to as the “GSM” chip, which enables field bars, battery state, etc. to be displayed on the screen and which may even be able to run games. In addition, in order to implement multimedia type functions via GSM radio communications terminals, there exist special components known as multimedia companion chips (MMCCs). Such components are endowed with very large signal processing capacity in order to enable multimedia applications of the audio or video types, for example, to be handled.
The technical problem which then arises relates to controlling the liquid crystal display screen when an MMCC is integrated in a conventional architecture for GSM terminals. There are now two microprocessors which must cohabit while processing information associated with controlling the screen.
Unfortunately, because companion chips require high display performance, they are connected directly to the screen and it is therefore these components which control access to the screen. It is thus commonly accepted that the MMCC must drive the control module of the liquid crystal display screen of the GSM radio communications terminal. To do this, such components generally possess internal random access memory (RAM) corresponding to the image on the screen and enabling them to process the image.
FIG. 2 shows such an architecture in which a multimedia companion chip 1 is connected to a GSM chip 2 via a serial link, the GSM chip 2 being provided to handle conventional functions associated with the GSM protocol. A parallel bus link is provided to transfer information between the MMCC 1 and a control module 3 which controls the liquid crystal display screen of the mobile radio communications terminal.
Energy saving is of crucial importance for the manufacturers of GSM radio communications terminals, and this involves a particular need to optimize battery life as well as possible for radio communications terminals while they are in standby mode, where standby mode is characterized by the terminal merely listening to the network and not transmitting anything. However, when the mobile radio communications terminal is in standby mode, the liquid crystal display screen needs to be refreshed regularly with information, in particular concerning the state of the network, the state of the battery, etc.
As mentioned above, integrating an MMCC in a GSM radio communications terminal leads to the architecture shown in FIG. 2 in which the screen control module is itself driven by the MMCC.
In the GSM standard, it is specified that the network should be listened to once every 2.5 seconds on average. Thus, when the radio communications terminal is in standby mode, the GSM chip potentially has information for forwarding to the MMCC once every 2.5 seconds.
The MMCC must therefore leave standby mode in order to implement the operation of refreshing the liquid crystal display screen. In all other cases, modes are implemented in which the companion chip is switched off. The companion chip then deactivates all of its non-necessary resources and remains in standby mode.
Nevertheless, compared with the architecture of a conventional mobile radio communications terminal in which the GSM chip drives the liquid crystal display screen directly via its control module, the architecture shown in FIG. 2 for a “intelligent” mobile radio communications terminal in which an MMCC is integrated thus requires its MMCC to be switched on even when the terminal is in standby mode, merely for the purpose of refreshing the liquid crystal display screen.
Thus, the fact of switching on the MMCC together with its memory merely to enable information relating to the state of the network to be displayed on the screen even though the companion chip is specifically designed for processing multimedia type information, has the consequence of considerably increasing energy consumption (in particular because of leakage currents) throughout standby operation during which it is necessary to implement operations of refreshing the screen.
An architecture for a mobile radio communications terminal of the kind shown in FIG. 2 in which the MMCC drives the control module of the liquid crystal display screen thus presents performance that is poor in terms of the energy consumption when the terminal is in standby mode.